Stirring the fermentation to increase attenuation

[JonGoku]

- Would stirring the yeast cake on the bottom of the fermentor have any bad side effects?

- Theoretically if you had a big enough motor and stir bar and could get the same effect of a normal stirplate would constantly stiring your wort in a 5-7.5 gallon glass carboy be best?

- I would assume oxidization would be one of the dangers, but if the stirring was done in a CO2 environment wouldn't this danger be nullified?

- I would also assume that this is not an easy yes or no answer because I know it is common practice to transfer the wort to a secondary to get it off the yeast cake for fermentations/conditioning that would be going for longer then 5-6 weeks. So where is the line (however fuzzy) drawn?

I am mainly just curious, but if stirring is not a bad thing, I might add a homemade stir rod into my next fermentation and occasionally manually stir it with magnet from the outside.

Penny for your thoughts.

Cheers!

[BrewMasterBrad]

Unless you are getting some very low attenuation already, why is this a concern? You would be better served to make sure you are pitching enough healthy yeast and controlling your fermentation temperature.

By no means should you ever contantly stir your fermenting beer. Even if you think you are in a pure CO2 environment, you are not and you will draw oxygen into the wort. Oxygenation would not be the concern then, it would be that the yeast would be aerobic and not fermenting. You would basically be making a giant yeast starter.

[brahn]

I agree with Brad, unless you're having major attenuation problems this really isn't relevant. Even if you are having attenuation problems I think there are better places to look like mash temperature, thickness and your grist composition.

The only time I've ever really considered trying to stir the yeast back up has been in big (1.100+) beers, and in my experience it hasn't been necessary there either.

Brent

[JonGoku]

Unless you are getting some very low attenuation already, why is this a concern? You would be better served to make sure you are pitching enough healthy yeast and controlling your fermentation temperature.

Well as of 3 days ago (7 days from pitching) my gravity was 1.024 and the target gravity is 1.017. The airlock was still breathing about a bubble every 2-3min so still slightly active but not excited. I was just curious about ways to help future such cases. Who knows it may be at a lower gravity when I check this evening, but I doubt it will have jumped down to 7 points at this stage in the ferment.

I was believe my temperature control has been pretty good as the fermetor has been sitting in a water bath with a constant temperature reading of 62-65*. The yeast I started with was a rehydrated dry yeast and I have been looking at beginning starters which turned me on to this possible concept of stirring an entire fermentor with a "similar" process although manual and for only a brief period.

By no means should you ever contantly stir your fermenting beer. Even if you think you are in a pure CO2 environment, you are not and you will draw oxygen into the wort. Oxygenation would not be the concern then, it would be that the yeast would be aerobic and not fermenting.

What if you were less "stirring" the beer, but disturbing the yeast cake some to push some of the yeast back into suspension and theoretically into activation.

You would basically be making a giant yeast starter.

This was kind of the point, but I didn't realize a "yeast starter" was inferior in taste, beyond normally only being made with DME.

[JonGoku]

I agree with Brad, unless you're having major attenuation problems this really isn't relevant. Even if you are having attenuation problems I think there are better places to look like mash temperature, thickness and your grist composition.

I wish that was a problem I have, but I'm still a noob doing extract.

[lars]

What if you were less "stirring" the beer, but disturbing the yeast cake some to push some of the yeast back into suspension and theoretically into activation.

Usually, the first yeast to drop out of suspension, do so because they are done (dead). While you may rouse some live yeast, I'd be a bit concerned about off flavors (unless you allow some additional settling time).

On another note, extract brews are notious for finishing high. This is mostly due to the extract making process that does a bit of damage to the fermentability of your wort. I have found that US05 dry yeast tends to ferment down lower than WL001, so if I were brewing extract, I'd be leaning towards using that yeast (it is a good all purpose yeast too, and I've been on a dry yeast kick for the last year or so).

[jward]

When I did extract brewing I poured a lot of trub into the fermenter. I would hesitate on mixing that crap into suspension. I was always glad to have the yeast cover it over.

[JonGoku]

When I did extract brewing I poured a lot of trub into the fermenter. I would hesitate on mixing that crap into suspension. I was always glad to have the yeast cover it over.

Why would it matter if you were doing extract compared to all grain on how much trub you end up pouring into the fermentor? Is the amount of trub from extract more then from AG or just the fact that you took less care when you were still new? Personally I try to leave as much behind as possible and with my last batch I used the handy dandy siphon tap that Kevin gave me.

I'm debating about using a screen as well to help trap trub and increase aeration.

[jward]

It's not a extract vs. all-grain issue. For me it was several things. I used to put more trub in the fermenter because I wanted to get every last drop of wort and that was the easiest way. Going to 10 gallon batches made it mentally OK to leave some wort (and more trub) behind. Actually, it's pretty easy to make a batch a little bigger for the purpose of having a little extra wort to leave behind. The other change was when I got a conical. Anything that will go through the pump I can let settle in the conical and easily drop the it out the bottom. With proper technique one can squeeze every last drop of wort, leave more trub behind no matter if all-grain/extract or the kind of fermenter.

[bwarbiany]

I need to rig up a screen in my boil kettle to catch hop matter & cold break. I usually recirc through the CFC in order to get the wort down to 100 deg or so before running it through the CFC into the fermenter, so I think I'd catch most of my cold break in the filter.

Of course, just getting a conical would fix my problem with trub.